From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fac41,9a0ff0bffdf63657 X-Google-Attributes: gidfac41,public X-Google-Thread: f43e6,9a0ff0bffdf63657 X-Google-Attributes: gidf43e6,public X-Google-Thread: 103376,4b06f8f15f01a568 X-Google-Attributes: gid103376,public X-Google-Thread: 1108a1,9a0ff0bffdf63657 X-Google-Attributes: gid1108a1,public From: ell@access.digex.net (Ell) Subject: Re: Software landmines (loops) Date: 1998/09/04 Message-ID: <35ef7dff.24318728@news.erols.com>#1/1 X-Deja-AN: 387749300 Content-Transfer-Encoding: 7bit References: <6sbuod$fra$1@hirame.wwa.com> <35f51e53.48044143@ <904556531.666222@miso.it.uq.edu.au> <6sgror$je8$3@news.indigo.ie> <6sh3qn$9p2$1@hirame.wwa.com> <6shbca$66c$1@news.indigo.ie> <6shhq7$lut$1@hirame.wwa.com> <6sjbso$1lk$2@news.indigo.ie> <6sjijg$36r$1@hirame.wwa.com> <6skhcm$1dr$2@news.indigo.ie> <6skqf3$9g0$1@hirame.wwa.com> <35f1f9fe.9111641@news.erols.com> <35f23ce2.7649859@news.erols.com> <6snn1b$c90$1@hirame.wwa.com> Content-Type: text/plain; charset=us-ascii X-Complaints-To: abuse@rcn.com X-Trace: winter.news.erols.com 904889830 10357 207.172.119.177 (4 Sep 1998 06:17:10 GMT) Organization: Universe Mime-Version: 1.0 Reply-To: ell@access.digex.net Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada Date: 1998-09-04T00:00:00+00:00 List-Id: "Robert Martin" wrote: > >Ell wrote in message <35f23ce2.7649859@news.erols.com>... > >> >>Think "avoid unstructured control flow", and not "avoid [creating code >>which has multiple exits]". >You had best define 'unstructured' in this context. Dijkstra's definition >of 'unstructured control flow' is control flow that does not conform >precisely to the four standard sequencing elements {sequence, selection, top >exit loop, bottom exit loop}, all of which have a single entry and a single >exit. Where is this documented? Where has Dijkstra stated that flow control must conform precisely to the 4 specific elements you mention? I know that sequence, selection, and *looping * are major appropriate flow control elements, but please show where Dijkstra says that "top exit loop" and "bottom exit loop" are, or should be standard flow control elements. >>That's the true spirit of one aspect of the structured paradigm as I >>see it. The other being that we should use abstractions to design >>code and to model functional domain processes. >> >>It was Dijkstra who said he thinks of *abstraction* when someone >>mentions "structured programming". >Indeed, Dijkstra talks about abstraction quite a bit in the book "Structured >programming". One of his uses of the term is that the four sequencing >elements he recommends can all be considered to be units whose internals >can, at times, be ignored (i.e. abstracted away) because they have a single >entry and a single exit. Please refer to relevant citations to back up this assertion. I have seen nothing that Dijkstra refers to explicitly about se/se on other than what you quoted about flowcharts. And this everyone knows is how to create flowcharts on a page - one entry point, one exit. Elliott